1. Field of the Invention:
The present invention relates to the hydrogenation of polyhydroxylunsaturated hydrocarbon polymers (hereinafter referred to as unsaturated polymers).
2. Description of the Prior Art:
It is known that saturated polymers produced by the hydrogenation of unsaturated polymers provide hard polymers which have high stability and at high temperatures deteriorate and exhibit a low degree of coloring. The polymers also possess high weather durability, ozone or oxidation resistance and light-fastness and have stable physical properties such as modulus, elongation and tensile strength. In the hydrogenation of the unsaturated polymers nickel and certain noble metals have been used as catalysts for the hydrogenation reaction. Catalysts of nickel or palladium have been practically used. However, when the nickel catalyst is used, the rate of the hydrogenation reaction is slow, especially so in the later stages of the hydrogenation reaction and so it is disadvantageous to use the catalyst from the economical viewpoint. When a palladium catalyst is used, the rate of the hydrogenation is high enough, however the palladium catalyst facilitates the removal of the terminal hydroxyl group from the polymer. Accordingly, when the resulting saturated polymer is cross-linked with a polyisocyanate, the cross-linking reaction is not smooth and the desired tight polymer useful for industrial purposes is difficult to obtain. Furthermore, the elimination of the hydroxyl group has not been prevented by varying the reaction conditions such as the temperature and the reaction period.
A need, therefore, continues to exist for a method of hydrogenating hydroxyl containing unsaturated polymers while avoiding the elimination of the terminal hydroxyl groups from the polymer.